1. Field of the Invention
The present invention relates to a technology of preparing fish embryos and producing fish individuals.
2. Description of the Related Art
In recent years, clones have been produced in various mammals by transplanting a somatic cell-derived nucleus into each unfertilized egg. In fish, triploid individuals were reportedly produced by methods such as transplanting an embryonic cell into unenucleated unfertilized eggs that is used as the recipient cell (Niwa et al., CLONING, Vol. 2, Number 1, p. 23-24, 2000). Further, clones are reportedly produced in a method such as transplanting an embryonic cell into enucleated unfertilized egg that is used as recipient cell (e.g. Japanese Patent Application Publication 2002-125517; Wakamatsu et al., PNAS, vol. 98, no. 3, pp. 1071-1078, 2001).
On the other hand, for more efficient production of individuals or of genetically engineered modified individuals in fish, the development of a method for producing fish individuals by nuclear transplantation using cultured cell-derived or somatic cell-derived nuclei has been awaited. Under such circumstances, there is a report in which with zebra fish, individuals were reportedly produced by transplanting a nucleus of an embryo-derived cultured cell into each enucleated unfertilized egg (Ki-Young Lee et al., Nature Biotechnology 20, p. 795-799, 2002). Further, in medaka (Oryzias laties), an attempt has been made to produce individuals by transplanting a cultured cell nucleus into each unenucleated unfertilized egg (B. Ju et al., Develop. Growth Differ. 45, p. 167-174, 2003). However, in the latter report, it is disclosed that some embryos hatched but failed to mature into adult fish, and malformed embryos were often found although the extent of malformation varied and that embryo-constituting cells were mosaic with respect to the chromosomal ploidy thereof.